Writing protection structure of a disk cartridge

ABSTRACT

A disk cartridge comprises a case with an upper and a lower shell halves united together to accommodate a disk of 3.5 inches therein, a guide portion, a shutter, and a slider slid in the guide portion of the case for supporting the shutter. The shutter is moved by a drive pin to open and close a head and spindle holes. The slider enables the shutter to move smoothly along the guide portion and prevents the shutter from being disconnected from the guide portion when the case is dropped.

This is a divisional application of U.S. Ser. No. 08/523,039, filed Sep.1, 1995, which is a continuation of U.S. Pat. No. 226,489, filed Apr.12, 1994 and now abandoned, which is in turn a divisional application ofU.S. Ser. No. 08/116,807, filed Sep. 3, 1993 and now granted as U.S.Pat. No. 5,325,257, which is a continuation of U.S. Ser. No. 07/654,897,filed Feb. 13, 1991 and now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a disk cartridge for accommodating a disktherein, and more particularly to a disk cartridge for accommodating adisk of 3.5 inches.

A disk-like recording medium used for a recording/reproducing apparatusis accommodated in a disk cartridge in order to prevent its breakage andattachment of dust thereonto. Such a disk cartridge comprises an upperand a lower shell halves to form a case in which the disk-like recordingmedium, e.g., a magnetic disk, an optical disk or the like. The case isprovided with a spindle hole for receiving a spindle to rotate the disktherein, and a head hole for receiving a head to read and writeinformation. There is provided, on the case, a shutter made of metal toprevent dust or dirt from coming into the case. The shutter is urged bya twist coil spring in a direction to close the two holes provided onthe case. The shutter is slidably moved by a drive pin provided in areading/writing apparatus, that is, a player to open and close the twoholes in the case.

However, in such a conventional disk cartridge, since the metallicshutter is attached directly to the case, the shutter cannot be slidsmoothly on the case. Further, since a guide portion for guiding theshutter is not arranged between the shutter and the case, the shuttercannot be guided correctly in its sliding direction.

In addition, there are some problems that the engagement of the case andthe twist coil spring is not made reliably, that an injection molding ofthe case is not made desirably, and that the shutter is disconnectedfrom the case when the disk cartridge is dropped.

SUMMARY OF THE INVENTION

In view of these problems, it is an object of this invention to provideda disk cartridge in which a shutter provided on a case can be smoothlyslid on the case.

It is another object of this invention to provide a disk cartridge whoseappearance is desirable and whose case is reliably held by apredetermined position in a player.

According to one aspect of this invention, there is provided a diskcartridge having a case for accommodating a disk of 3.5 inches therein,a shutter provided slidably on the case in a bent manner for opening andclosing a head hole for receiving a reading/writing head and a spindlehole for receiving a spindle for rotating the disk, and a spring memberfor urging the shutter in its closing direction, which comprises aslider which is provided slidably in a guide portion of the case andonto which the shutter is fixed.

According to another aspect of this invention, there is provided a diskcartridge having a combination of an upper and a lower shell halves foraccommodating a disk, wherein each shell half is made by injectionmolding through a mold having a single injection hole.

Further objects, features and other aspects of this invention will beunderstood from the following detailed description of the preferredembodiments of this invention with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a disk cartridge of this invention asviewed from the side of an upper shell half;

FIG. 2 is a perspective view of a disk cartridge of this invention asviewed from the side of a lower shell half;

FIG. 3 is a front view of the disk cartridge when a shutter is moved toopen a spindle and a head holes;

FIG. 4 is a perspective view of a slider;

FIG. 5 is a front sectional view of a guide portion of the diskcartridge;

FIG. 6 is a plan view of the guide portion thereof;

FIG. 7 is an explanatory view showing a state of the guide portion whenthe shutter takes its opening position;

FIG. 8 is a view as viewed from an arrow A in FIG. 7;

FIG. 9 is a sectional view taken along the line IX--IX in FIG. 5;

FIG. 10 is a view as viewed from an arrow B in FIG. 7;

FIG. 11 is a sectional view taken along the line XI--XI;

FIG. 12 is a plan view of a front end of the guide portion thereof;

FIG. 13 is a perspective view of the front side of a slider;

FIG. 14 is an explanatory view showing a state where a head is insertedinto the cartridge with the shutter taking its opening position;

FIG. 15 is a longitudinally sectional view showing a state of engagementbetween the shutter and the case;

FIGS. 16 and 17 are sectional views of the front and back sides of theguide portion as other embodiment of the slider, respectively;

FIG. 18a is a view of the inner surface of a spring receiving portionfor receiving an end of the twist coil spring;

FIG. 18b is a perspective view of the spring receiving portion;

FIG. 19 is a perspective view of another spring receiving portion on thefront end of the case for receiving one end of the twist coil spring;

FIG. 20 is a perspective view of the front side of the guide portionthereof;

FIG. 21 is a perspective view of the front side of the guide portion asother embodiment;

FIG. 22 is a plan view of the guide portion in FIG. 21;

FIG. 23 is a sectional view taken along the line XXIII--XXIII;

FIG. 24 is a front view of a twist coil spring provided at an innercorner of an upper shell half, showing other embodiment of the twistcoil spring;

FIG. 25 is a plan view of a slider with a shutter;

FIG. 26 is a side view of the slider;

FIG. 27 is a longitudinal view of the slider, showing an engagementbetween the shutter and the slider;

FIG. 28 is a plan view showing other embodiment of the guide portion;

FIG. 29 is a longitudinal view of the guide portion in FIG. 28;

FIG. 30 is a sectional view taken a long the line XXX--XXX;

FIG. 31 is a plan view of the lower shell half of the disk cartridge;

FIG. 32 is a perspective view of the inner surface of the upper shellhalf of the disk cartridge;

FIG. 33 is a perspective view of the inner surface of the lower shellhalf of the disk cartridge;

FIG. 34 is a sectional view taken along the line XXXIV--XXXIV;

FIG. 35 is a perspective view of a plurality of locating pins providedin a player;

FIG. 36 is a sectional view taken along the line XXXVI--XXXVI;

FIG. 37 is a perspective view of a writing protection mechanism on theside of the lower shell half;

FIG. 38 is a plan view of the writing protection mechanism;

FIG. 39 is a perspective view of the writing protection mechanism asviewed from the lower shell half;

FIG. 40 is a perspective view of a block used for the writing protectionmechanism;

FIG. 41 is a diagrammatic view of a metal mold for manufacturing eachshell half;

FIG. 42 is a plan view of a cavity in the metal mold; and

FIG. 43 is a diagramatic view of another metal mold for manufacturingeach shell half.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1 and 2, a reference numeral 1 shows a case of a disk cartridgemade of synthetic resin, which comprises an upper and a lower shellhalves 1a, 1b which have, as a whole, shallow box-like shapes,respectively.

In the case 1 is accommodated, e.g. an optical disk 2 of 3.5 inches forrecording optical information thereon. At the center of the lower shellhalf 16 is provided a spindle hole 4 for receiving a spindle (not shown)to rotate the optical disk 2 accommodated in the case 1 when thecartridge is loaded into a player (not shown), and a hub 2a fixed ontothe center portion of the disk 2 is opposed to the spindle hole 4. Theupper and lower shell halves 1a, 1b have head holes 3, 3 for receivingan optical head h for reading information recorded on the disk 2 and forwriting information thereonto (FIGS. 3 and 14).

When reproduction is not performed, the two holes 3, 4 are closed by ashutter 5 to protect insertion of dirt or dust into the case 1. Theshutter 5 is formed in such a manner that a thin metal plate such as astainless steel plate is bent, at a center base portion 5a thereof, inthe shape of a letter U to form a main closing plate 6 for opening andclosing the head and spindle holes 3, 4 in the lower shell half 1b and asupplementary closing plate 7 having a length shorter than the mainclosing plate 6 for opening and closing the head hole 3 in the uppershell half. The main closing plate 6 of the shutter 5 and thesupplementary closing plate 7 thereof can be slidably moved in a shallowrecess R₁ formed on the lower shell half 1b and in a shallow recess R₂formed on the upper shell half 1a, respectively. The distal end of thesupplementary closing plate 6 is guided along a retaining plate 40 so asnot to be raised therefrom. In FIG. 1, the distal end of thesupplementary closing plate 7 is not guided by a retaining plate becauseof its short length, and, however, if necessary, a retaining plate 41 asindicated by an imaginary line may be provided.

At the front end of the case 1 is formed a guide portion G for guidingthe shutter 5, which has a guide surface 8 extending horizontally on theleft side as viewed in FIG. 3. On the right side of the guide surface 8is formed a dropping recess 9 into which a drive pin P provided in theplayer (not shown) is dropped when the shutter 5 is moved by the drivepin P to open the head and spindle holes 3, 4. The drive pin P moves theshutter 5 to the right, as viewed in FIG. 3, to open the two holes 3, 4.

A slider 12 made of synthetic resin such as polyacetal is fixed to theinner surface of the base portion 5a of the shutter 5 and slidablyaccommodated in the guide portion G. The right half portion of theslider 12 is fixed by a plurality of tapping screws to the inner surfaceof the base portion 5a thereof. The guide portion G comprises the aboveleft guide surface 8, a right guide surface 212 and a connecting portion31 provided between the both guide surfaces 8, 212.

The slider 12 is, as shown in FIG. 4, has a long-bar like shape and arectangular shape in section. The slider 12 comprises a shutter supportportion 21 located inside of the base portion 5a of the shutter 5 forsupporting the shutter 5, and an extended portion extended from one endof the shutter support portion 21 and having a small thickness t₁. Thethickness t₁ of the extended portion 22 is smaller than the thickness t₂of the shutter support portion 21. The shutter support portion 21 has afirst engaging projection body 23 at its right end, as viewed in FIG. 4,and the extended portion 22 has a second engaging projection body 24 atits left end. The second engaging projection body 24 comprises a slidingguide piece 25 provided at the left end of the extended portion 22 so asto be extended in the left and right directions. In this manner, thefirst and second engaging projection bodies 23, 24 are extended from theright end of the shutter support portion 21 and the left end of theextended portion 22 in the longitudinal direction of the slider 12, and,therefore, the two engaging portions 23, 24 of the slider 12 forengaging with the guide portion G of the case 1 are separated widelythereby to slidably guide the shutter 5 in a stable manner.

As shown in FIGS. 4, 11, 12 and 13, the first engaging projection body23 has a pair of projections 23a, 23b on its opposite sides, which areengaged with a pair of guide grooves 27a, 27b (FIG. 11) formed on theinner walls of the upper and lower shell halves 1a, 1b in the slidingdirection of the slider 12. One projection 23a is formed long while theother projection 23b is formed short. The first engaging projection body23 has a first spring receiving portion 15 for receiving one arm 14a ofa twist coil spring 14 which is accommodated in a spring accommodatingspace 17 (FIGS. 2 and 12). The first spring receiving portion 15 has aprojection 15a for preventing the one arm 14a from coming out of thefirst spring receiving portion 15 (FIG. 13). The first spring receivingportion 15 has, at its one side, an opening w for receiving a bentdistal end 14c of the one arm 14a as shown in FIG. 13. The bent distalend 14c thereof is inserted into the opening w thereby to protectdisconnection of the one arm 14a from the first spring receiving portion15. The case 1 has, at its upper right corner, as viewed in FIG. 18, asecond spring receiving portion 16 for receiving the other arm 14b ofthe spring 14 which urges the slider 12 to the left as viewed in FIG.18. As shown in FIG. 18, the first engaging projection body 23 has adividing groove 23c into which the twist coil spring 14 is inserted.

In contrast, the extended portion 22 of the slider 12 is, as shown inFIG. 6, extended from the base portion 5a of the shutter 5 to the left,as viewed in FIG. 6, to abut against the drive pin P. The drive pin Pabuts against the distal end of the extended portion 22 to push it inthe right direction when the shutter 5 is moved to open the two head andspindle holes 3, 4. Therefore, any other specific portion for engagingthe drive pin P is not necessary because the extended portion 22 of theslider 12 functions as an engaging portion for engaging the drive pin P.This simplifies the structure of a portion of the shutter 5 which isfixed onto the slider 12 thereby to make its outer shape small. Further,the reason why the thickness t₁ of the extended portion 22 is small isbecause the extended portion 22 does not obstruct the approach of thehead h toward the head hole 3 when the head h is inserted thereinto.That is, the head h is, as shown in FIG. 14, moved toward the head hole3 from the side of the guide portion G. The lower face h₁ of the head his located, at its height position, close to the surface of the disk 2accommodated in the case 1. The connecting portion 31 at the front endof the case 1 is opposed to the extended portion 22 when the shutter 5takes its opening position and cut thinly to form a thin wall with athickness t₃ (FIG. 6). The thickness t₃ is determined so as to permitthe lower face h₁ of the head h to pass in a recessed portion of theextended portion 22. The thickness t₁ of the extended portion 22 isslightly smaller than the thickness t₃ of the recessed portion of theconnecting portion 31 and the length l₂ of the extended portion 22 isslightly longer than the length l₁ of the recessed portion of theconnecting portion 31. However, the thickness t₁ and the length l₂ ofthe extended portion 22 may be equal to the thickness t₃ and the lengthl₁ of the recess forming part of the connecting portion 31,respectively.

The sliding guide piece 25 of the second engaging projection body 24,formed at the distal end of the extended portion 22 of the slider 12slides on the guide surface 8. The extended portion 22 has, at its leftend, a guide foot 26 formed integratedly with the distal end of theextended portion 22. The guide foot 26 engages with a pair of guiderails 28a, 28b to guide the slider 12 in its sliding direction and toprevent the slider 12 from being disconnected from the guide portion Gof the case 1.

The sliding guide piece 25 has, at its end, a pair of wings 25a, 25bprojecting in its lateral direction, whose lower surfaces slidablycontact the guide surfaces 8a, 8b. The wings 25a, 25b have chamferedsmoothly curved corners 25c, 25d; 25e, 25f located separately in thesliding direction of the slider 12, respectively. The two droppingrecesses 9, 9 provided on the respective guide surfaces 8a, 8b have alsochamfered corners 9a, 9b, 9c, 9d at their respective opposite sides(FIGS. 7 and 8).

The second engaging projection body 24 has an upper surface which islocated at a position lower than the bottom walls of the droppingrecesses 9 when the shutter 5 is moved to open the head and spindleholes 3, 4. The guide foot 26 has, at its rear end, an inclined surface26c which is opposed to the outer surface of a surrounding wall 32 forholding the periphery of the disk 2 when the shutter 5 takes itscomplete opening position.

When the shutter 5 is moved to open the holes 3, 4 of the case 1, thedrive pin P is, as shown in FIG. 7, engaged with the front end of thesliding guide piece 25 of the slider 12 to push the slider 12 to theright so that the slider 12 is slidingly moved on the guide surfaces 8a,8b. At this time, the slider 12 is slidingly moved in a state whereinthe sliding guide piece 25 and the first engaging projection body 23 areguided by guide rails 8a, 8b; 28a, 28b (FIG. 9) thereby to move theshutter 5 to the right to open the head and spindle holes 3, 4. When theshutter 5 takes its complete opening position, the drive pin P dropsinto the dropping recess 9 to maintain the shutter 5 at its openingposition. If the upper surface 26a of the guide foot 26 is located morehighly than the bottom wall of the dropping recess 9, the dropping pin Pabuts against the upper surface 26a of the guide foot 26 to be preventedfrom dropping completely into the dropping recess 9. As a result, thedrive pin P is not reliably held by the dropping recess 9 to be pushedout of the dropping recess 9 by the slider 12 urged by the twist coilspring 14. However, in this embodiment, since the upper surface 26a ofthe guide foot 26 is located at a position lower than the bottom wall ofthe dropping recess 9 as shown in FIGS. 7 and 8, the drive pin P can bereliably dropped into the dropping recess 9.

Further, since the guide foot 26 has the inclined surface 26c at itslower face, the guide foot 26 does not contact the surrounding wall 32when the shutter 5 takes its complete opening position.

When the slider 12 is slid on the guide surfaces 8a, 8b to open the twoholes 3, 4, the wings 25a, 25b pass over the dropping recesses 9, 9 inthe extending direction of the guide surfaces 8a, 8b. At this time, ifthere is an error in manufacture of the second engaging projection body24 and the guide surfaces 8a, 8b, etc., the corners 25d, 25f may becaught by the corners 9c, 9d of the walls of the dropping recesses 9, 9.However, since the corners 25d, 25f of the wings 25a, 25b and thecorners 9c, 9d of the dropping recesses are chamfered with each other,the wings 25a, 25b can be smoothly passed over the dropping recesses 9,so that the shutter 5 can be smoothly moved to the limit to open theholes 3, 4 completely.

In contrast, when the two holes 3, 4 are opened, the drive pin P isremoved upwardly from the dropping recesses 9 to return the slider 12 toan original position under a spring force of the twist coil spring 14(FIGS. 7 and 8). Also, at this time, since the corners 25c, 25e of thewings 25a, 25b and the corners 9a, 9b of the dropping recesses 9, 9 arechamfered, the wings 25a, 25b can pass over the dropping recesses 9, 9smoothly.

The drive pin P of the player is adapted to be projected into the casefrom the right to the left as viewed in FIG. 10, and, however, there maybe a player whose drive pin P does not project sufficiently because ofan error in its manufacture. If, in such a player, the drive pin P isstopped at a position P₁, a part of the drive pin P is located beneaththe wing 25b. Therefore, the drive pin P may be caught by the wing 25bwhen it is moved upward to close the two holes 3, 4. In this case, thecorner 25e of the wing 25b is chamfered, and, therefore, the drive pin Pcan be moved slidingly on the corner 25e without being caught by thecorner 25e.

Furthermore, as shown in FIG. 10, suppose that the drive pin P₁ isstopped at the position P₁. At this time, if a arm 33 for supporting theguide foot 26 is formed so as to have a width W₀ smaller than the widthW₁, there may be a case that the drive pin P does not reliably engagewith the front surface of the arm 33. As a result, the slider 12 isreturned to the original position under the repulsive force of the twistcoil spring 14, so that the shutter closes the two holes 3, 4 bymistake. However, the arm 33 of the slider 12 is so formed as to havethe width W₁ which is approximately equal to one third of a total widthT of the case 1, and, therefore, the drive pin P₁ can engage reliablywith the arm 33 thereby to reliably hold the shutter 5 at its openingposition.

In contrast, as mentioned above, when the two holes 3, 4 are completelyopened, as shown in FIG. 18, the first engaging projection body 23 mayabut against the other arm 14b of the twist coil spring 14. However, theother arm 14b does not abut against the projection 23b because theprojection 23b is cut away to be formed shortly. When the coil spring 14is pushed to open the two holes 3, 4, the one arm 14a is, as shown inFIG, 13 inserted into the dividing groove 23c. However, at this time,there may be a case that the one arm 14a is caught by the inner corners23f, 23g at the front end of the projection 23a. Since the corners 23f,23g are chamfered, the one arm 14a does not be caught thereby. Further,two inner corners 23h, 23i of the short projection 23b are alsochamfered to ensure smooth movement of the one arm 14a.

The operation or effect of the first engaging projection body 23 willnow be explained in more detail.

When the slider 12 is moved slidingly to the right, the twist coilspring 14 is pushed to rotate the one arm 14a in the clockwise directionA about the bent end 14c. At this time, even if the one arm 14a happensto abut against the front corner 23f of the projection 23a, it can slideon the chamfered front corner 23f without being caught thereby tosmoothly come into the dividing groove 23c. In contrast, as mentionedabove, the other arm 14b does not abut against the short projection 23bas shown in FIG. 18(a).

When the shutter 5 takes a closing position, the slider 12 is slid tothe left, as viewed in FIG. 12, to release the spring from its pushedstate thereby to rotate the one arm 14a in the counterclockwisedirection B (upwardly) about the bent end 14c. At this time, even if theone arm 14a happens to abut against the front inner corner 23g, it canslide thereon because it is chamfered to ensure a smooth rotatingmovement of the one arm 14a. In this manner, if the four corners 23f,23g, 23h, 23i located at an inlet of the dividing groove 23c arechamfered, a smooth rotating movement of the one arm 14a can be ensuredduring movement of the shutter 5.

FIGS. 16 and 17 show a slider which can be easily assembled into theguide portion G of the case 1. That is, the first and second engagingprojection bodies 23, 24 have two dividing grooves 23d and 26c extendingthrough total length of each body in its longitudinal direction. Thedividing groove 23d is formed so that the dividing groove 23c isextended in the longitudinal direction of the second projection body 23.The projections 23a, 23b have, at their lower faces, two inclinedsurfaces 23s, 23s, in cross section, respectively, while the guide foot26 has, at its lower face, two inclined surfaces 26s, 26s in crosssection. The formation of the dividing grooves 23d, 26c of the twobodies 23, 24 ensures an elastic deformation of the projections 23a, 23bof the first engaging projection body 23 and the two portions divided bythe dividing groove 26c of the second engaging projection body 24 whenthe two bodies 23, 24 are pushed into the guide portion G while passingover the guide rails 212a, 212b, 28a, 28b. Accordingly, the first andsecond engaging projection bodies 23, 24 can be easily pushed into aspace between the guide rails, and the lower ends of the first andsecond engaging projection bodies 23, 24 are caught by the lowersurfaces of the guide rails to be prevented from coming out of the guideportion G of the case 1. If this slider is used, it is not necessarythat the slider 12 is put between the upper and lower shell halves 1a,1b when the case 1 is assembled. That is, the slider 12 shown in FIGS.16 and 17 can be assembled into the guide portion G thereof only bypushing the slider 12 thereinto after the case 1 is assembled.

The shutter support portion 21 has, as shown in FIGS. 4 and 5, at itsupper face, two screw holes 21a, 21a each of which has a bowl-likerecess, and the base portion 5a of the shutter 5 has two bowl-likerecesses 5a, 5b, corressponding to the screw holes 321a, 21a, whichformed through pierce press working. When the recesses 5b of the shutter5 are engaged with the screw holes 21a of the slider 12, the slider 12is reliably located to the shutter 5. Thereafter, a tapping screw 16(connecting member) is passed through the screw hole 5a and the recess5b to fix the shutter 5 to the slider 12. The head of the tapping screw16 is accommodated in the bowl-like recess 5b to prevent the head fromprojecting upwardly. Therefore, a finger does not get injured due totouching the head of the tapping screw 16.

Further, as shown in FIG. 15, the main closing plate 6 of the shutter 5and the supplementary closing plate 7 are so formed that they are urgedto come close to each other. This structure prevents the shutter 5 frombeing removed from the case 1 and increases a sealing property of theshutter 5 with respect to the case 1.

In FIGS. 18 (a) (b), on the side of the upper shell half 1a of thesecond spring receiving portion 16 is formed a guide hole 42 fromaccommodating a bent end 14d of the twist coil spring 14. The hole 42 isformed by a lower projection 41 and a guide piece 43 opposed to thelower projection 41 so as to be inclined upwardly. The other arm 14b ofthe twist coil spring 14 is reliably held by the second spring receivingportion 16. As shown in FIG. 19, in order to guide the other arm 14binto the second spring receiving portion 16, a guided plate 51 with anobliquely cut away portion at its front end may be extended from one endof a notch into which the drive pin P is accommodated.

When a one-side disk cartridge is inserted upside down into the player,the drive pin P is operated by mistake. In order to prevent this wrongoperation, a pair of notches 10a, 10b into which the drive pin P can beinserted are, as shown in FIG, 20, formed at the guide portion G. Thenotches 10a, 10b are formed so as to cut away a pair of wrong operationprevention walls. A pair of wrong operation prevention walls 11a, 11bhave a height much larger than the height of the drive pin P which islocated in the notches 10a, 10b or have a minimum height at which thedrive pin P is held.

When the disk cartridge is inserted upside down, the drive pin isinserted into the notches 10a, 10b without engaging with the front endof the second engaging projection 24 of the slider 12. A force isexerted on the drive pin P to be moved to the left as viewed in FIG. 20.However, since each of the walls 11a, 11b has a sufficient height, thedrive pin P cannot come out of the notches 10a, 10b. Therefore, thecartridge cannot be inserted into the player any more thereby to preventbreakage of the player or the cartridge.

In FIGS. 21 and 22, the wrong operation prevention wall 11a on the sideof the upper shell half 1a has a height close to the inner surface ofthe base portion 5a of the shutter 5, and a wrong operation preventionwall 11c on the side of the lower shell half 1b has a height smallerthan that of the wall 11a.

In this case, the shape of a slider 70 is different from that mentionedabove. That is, one side face of the slider 70 faces, as shown in FIG.23, the inner surface of the wall 11a, a portion of the slider 70 ridesslidably on the wall 11c to form two sliding surfaces 11d, 70a. Theslider 70 and the walls 11a, 11c are made of synthetic resin such aspolycarbonate, polyacetal, etc., and the two sliding surfaces 11d, 70dhave a slippery property, respectively. In this manner, the side face ofthe slider 12 is projected over the wall 11c to form a sufficientportion for receiving the bent end 14c for the spring 14. This structurecan prevent the bent end 14c from coming out of the first springreceiving portion 15.

The side face of the slider 12 has a projection guide rail with theinner surface of the guide portion G having a groove for engaging theguide rail as shown in the above embodiments. In contrast, the innersurface of the guide portion G may have a guide rail with the slider 12having a groove for engaging the guide rail.

As shown in FIG. 24, a twist coil spring 80 has a pair of arms 80a, 80bwhich are bent inwardly (in a direction of the center line L) to eachyouth and have two bent points 80c, 80d, respectively. Further, thespring 80 has a coil portion 80e between two arms 80a, 80b.

When the shutter 5 is moved to the right as shown in FIG. 24, the twistcoil spring 80 is pushed inwardly and the two arms 80a, 80b are moved tothe right side face of the case. At the side face of the case isprovided a drawing recess 1e with which a drawing member provided in theplayer is engaged to draw the case into the player when the diskcartridge is loaded in the player. At this time, the arm 80b does notabut against the inner wall of the drawing recess 1e projected inwardlybecause it is bent inwardly thereby to prevent the arm 80b from comingout of the second engaging portion 16.

In addition, if the two arms 80a, 80b bent inwardly to each other, astress exerted on the spring when the spring 80 is pushed inwardly isdispersed on the two bent points 80c, 80d without being concentratedonly on a single portion of the coil portion 80e. However, since aconventional spring has two straight arms, a stress is concentrated onlyon its coil portion. Therefore, since, in this embodiment, it can beeffectively avoided that a stress is concentrated only on a singleportion of the coil portion 80e, the coil portion 80e can have a longlife span.

Engagement between the slider 12 and the base portion 5a of the shutter5 may be as follows.

The slider 12 has, on the support portion 21, two projections 90a, 90bwhich are engaged with two recessed holes 26, 26 formed in the baseportion 5a of the shutter 5 (FIGS. 25 to 27). After engagement of theholes 26, 26 and the projections 90a, 90b is made, the projections 90a,90b projected upwardly are caulked by a caulking chisel to fix theshutter 5 onto the slider 12. The caulked head is not projected upwardlyover the surface of the base portion 5a because it is accommodated inthe recessed hole 26.

In the above embodiment, the one arm 14a of the twist coil spring 14 isengaged with one end of the slider 12. However, as shown in FIGS. 28 to30, a base portion 5a of the shutter 5 is extended forwardly to form aspring receiving portion 100 for receiving the one arm 14a of the twistcoil spring 14. In this case, the bent end 14c of the twist coil spring14 must be positioned over the upper surface of the wrong operationprevention wall 11c, and, therefore, the wrong operation prevention wall11a is higher than the wrong operation prevention wall 11c.

In this manner, if the spring receiving portion 100 is formed at one endof the base portion 5a of the shutter 5, assembly of the spring 14 andthe shutter 5 is facilitated. In this case, both sides of the one end ofthe base portion 5a thereof are extended downwardly in a frame-likemanner to form a sliding engagement portion 5b which is engaged with twoside groove 500, 500 on the guide portion G.

In FIGS. 31 to 34, the upper and lower shell halves 1a, 1b are united bya plurality of fastening parts U, U, . . . U which are jointed by fourscrews 110. That is, a screw hole 111 is formed on the lower shell half1b to receive the screw 110, and an accommodating recess 112 is formedat the head portion of the screw hole 111 in order to accommodate thehead of the screw 110 without protruding of the head from theaccommodating recess 112. A lower boss 113 is formed, at the peripheryof the screw hole 111 in the lower shell half 1b, so as to be extendedtoward the upper shell half 1a. A portion of the upper shell half 1a.corresponding to the screw hole 111 is formed an upper boss portion 114whose outer diameter is approximately equal to the inner diameter of thelower boss portion 113, so that the upper and lower boss portions aretightly engaged. The upper boss portion 114 is inserted into the lowerboss portion 113, and the screw 110 is then inserted into a screw hole115 through the screw hole 111 whereby the upper and lower shell halves1a, 1b are tightly united by a simple operation.

When the disk cartridge is loaded into the player, the case 1 is, asshown in FIG. 35, supported, at a predetermined position therein, byfour support pins 120, 120, . . . 122. One pair of support pins 120, 120are in the form of a column and the other pair of support pins 122, 122have two pins 122a, 122a on the upper surfaces of two columar bodies,respectively. That is, the case 1 is supported on four support pins withthe lower shell half 1b contacting the support pins 120, and the head ofeach support pin 120 abuts against a support place 123 located near theperiphery of the case 1.

The accommodating recesses 112 must be formed on the periphery of thelower shell half 1b, and the support places 123 must be also formed onthe periphery of the lower shell half 1b. Therefore, there may be a fearthat the recesses 112 and the support places 123 falls on each other.However, in this embodiment, there is no fear that the accommodatingrecesses 112 falls on the support places 123 because the support places123 are formed sufficiently remotely from the recesses 112 not only onthe upper side of the lower shell half 1b, but also on the lower sidethereof. Therefore, especially the heads of the support pins on theupper side of the case is not inserted into the accommodating recess112. Accordingly, the head of each support pin reliably abuts againsteach support place 123 thereby to support the cartridge at apredetermined position in the player.

As shown in FIG. 31, the case 1 has a pair of locating openings 130, 131on the both widthwise side of the case 1 in the two support places 123for receiving the locating pins 122a, 122a (FIG. 35). The right locatingopening has a circular shape while the left locating opening 131 has anelliptic shape to receive the pin 122a loosely. Therefore, even if thedistance between the two locating openings 130, 131 is slightlydifferent from a standard value, the pins 122a can be smoothly insertedinto the locating openings 130, 131. Each support place 123 is formedflatly because it functions as a reference plane when the disk cartridgeis loaded into the player.

On the lower side of the lower shell half 1b is formed a label attachingshallow recess 130 which is slightly recessed from the surface of thelower shell half 1b (FIG. 31).

The main closing plate 6 of the shutter 5 is slightly smaller in widththan the supplementary closing plate 7 and has a projection 140 at itsupper right corner. This is because a stopping wall 141 defining theshallow recess R₁ must be separated sufficiently from the outer sideperiphery of the case to form a sufficiently large support place 123.That is, it is desirably that the width of the base portion 5a of theshutter 5 is large in view of a stable sliding movement. To this end,the upper portion of the main closing plate 6 has the same width as thatof the supplementary closing plate 7, and the width of the main closingportion 6 is slightly narrow in comparison with that of thesupplementary closing plate to ensure a sufficiently large support place123. The stopping wall 141 has, at its upper corner, a cut away portion700 for engaging with the projection 140 of the supplementary closingplate 7.

On the right and lower side of the case 1 is provided a writingprotection mechanism 160 for preventing new information from beingrecorded on old information, that is, the writing protection mechanism160 has a first and second passing holes 213a, 213b through which alight beam emitted from a light emitting element passes to operate alight receiving element. The light beam is shielded by a closing piece215 (FIGS. 36 to 39).

The closing piece 215 has a main body 216 and two engaging legs 217a,217b extended from the opposite sides of the main body 216. The engaginglegs 217a, 217b have, at their ends, two projected portions 217c, 217d,respectively. The closing piece 215 is slidably accommodated in anaccommodating wall 218. The accommodating wall 218 on the lower shellhalf side has, at its inner surface, two stopping projections 218a, 218bto engage with the engaging legs 217a, 217b. When the projected portions217c, 217d of the engaging legs 217a, 217b are engaged with the uppersides of the stopping projections 218a, 218b, the main body 216 is heldto close the first and second passing holes 213a, 213b. When the closingpiece 215 is moved downwardly from a position shown in FIG. 38, theprojected portions 217c, 217d of the engaging legs 217a, 217b is engagedwith the lower sides of the engaging projections 218a, 218b, resultingin that the main body 216 opens the first and second passing holes 213a,213b to be held at its opening position. On the opposite sides of thepassing hole 213b on the lower shell half 1b is formed two insertiongrooves 505, 505 into which a pin is inserted to move the closing piece215.

There may be a case that the upper and lower shell halves 1a, 1b areassembled with a small space t therebetween by mistake. In addition,when the disk cartridge is dropped, there may occur the space t. In thiscase, the small space t does not influence the sliding movement of theclosing piece 215 because of sufficient thickness of the closing piece215.

In the case of a disk cartridge for accommodating a Hi-ROM disk, etc.,since such a writing protection mechanism is not necessary, a block 200is used as shown in FIG. 40. The block 200 has a projecting table 201 ona base 202. The projecting table 201 is inserted into the passing hole213b formed in the lower shell half 1b and the base 202 is accommodatedin a accommodating space defined by the surrounding walls 218. Thepassing hole 213a on the upper shell half 1a is always closed. Theaccommodated state of the block 200 in the mechanism 16 is indicated byan imaginary line as shown in FIG. 36.

As shown in FIGS. 32 and 33, at the periphery of the spindle hole 4 ofeach shell half are provided two annular projections 205, 206 which arecoated with a slippery material to prevent a wear between the disk andthe case.

Each of shell halves 1a, 1b is formed by a mold through an injectionmolding method, and the mold is, as shown in FIG. 41, formed by twodivided molds 300, 300. Injection material is injected into a cavity 301through a single injection hole 302. For example, in the case of thelower shell half 1b, the injection hole 302 is opposed to a positioncovered with the retaining plate 40 for retaining the distal end of themain closing plate 6 (FIG. 2). If an injection molding is performedthrough a plurality of injection holes, a wave-like pattern which iscalled a weld mark is formed at a joint place of materials supplied fromdifferent injection holes. However, if an injection molding is performedthrough the single injection hole 302 in this embodiment, a weld markdoes not occur.

As shown in FIG. 42, a cavity forming surface of each shell half,corresponding to the guide portion G of the case is polished in thesliding direction of the slider 12, that is, in the left and rightdirection as viewed in FIG. 42, to form a smooth surface for the slider12.

At last, as shown in FIG. 43, a mold 300 is provided with a pininjection adjusting mechanism for adjusting length of projection of aplurality of injection pins 500, 500 . . . 500. The mechanism comprisesa base 501 whose movement in the left and right direction can beadjusted. The length of projection of the pins 500 is adjusted so as notto form a trace of the injection pin 500 on the each shell half afterits injection molding.

What is claimed is:
 1. A structure of a case for accommodating a disktherein, which comprises two shell halves assembled with each other toform the case, each shell half having a spindle insertion hole forreceiving a spindle for rotating a disk and a head insertion hole forreceiving a head, one shell half having a first hole at a cornerthereof, the other shell having a second hole opposed to one side of thefirst hole, a closing piece being accommodated in an accommodating spacedefined by two accommodating walls so as to be moved from a firstposition to close the second hole to a second position to open thesecond hole, the closing piece comprising a main body which has asufficient size and height to close the second hole and at least one legprojected, in a moving direction of the closing piece, from a bottom endof the main body to locate the closing piece at the first or secondposition, cooperating with an inner surface of an accommodating wallwhich is provided on the shell half having the second hole; the firsthole receiving a head portion projected from the main body, twoinsertion grooves being provided on opposite sides of the first hole inthe moving direction of the closing piece to receive a pin as a toolinserted between a groove and a side face of the head portion of themain body, located in the first hole when the closing piece is moved. 2.A structure according to claim 1, wherein a block is accommodated,instead of the closing piece, in an accommodating space between the twoholes so that a projection table of the block is received to cover thewhole area of the first hole therewith.
 3. A structure according toclaim 1, wherein the closing piece has two legs projected from theopposite sides of the main body, each leg being provided with aprojected portion which is engaged with a stopping projection formed onthe inner surface of the accommodating wall.
 4. A structure according toclaim 1, wherein the stopping projection has almost a length of adistance between the projected portion and the main body.